Tropical Storm MARTY

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TROPICAL STORM MARTY DISCUSSION NUMBER 11
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL EP162009
200 PM PDT FRI SEP 18 2009
DEEP CONVECTION IS NOW CONFINED TO A SMALL AREA WEST OF THE CENTER
OF MARTY...AS INCREASING VERTICAL SHEAR APPEARS TO BE TAKING A TOLL
ON THE SYSTEM. A QUIKSCAT PASS FROM 1355 UTC SHOWED A FEW
BELIEVABLE 35-KT AMBIGUITIES...AND THIS IS THE BASIS FOR THE
INITIAL INTENSITY FOR THIS ADVISORY. IF THE CONVECTION CONTINUES TO
DECREASE...MARTY SHOULD BEGIN TO WEAKEN TONIGHT. THE SHIPS MODEL
CONTINUES TO SHOW THE CYCLONE MOVING INTO A MORE HOSTILE
ENVIRONMENT WITHIN THE NEXT 24 HOURS...WITH VERTICAL SHEAR
INCREASING TO OVER 30 KT BY THAT TIME. THE SHEAR...ALONG WITH A
LESS FAVORABLE THERMODYNAMIC ATMOSPHERIC AND OCEANIC ENVIRONMENT
SHOULD RESULT IN MARTY BECOMING A REMNANT LOW IN 24 TO 36 HOURS.
MOST OF THE GLOBAL MODELS SHOW THE REMNANT LOW DISSIPATING BY 3
DAYS.
SEVERAL MICROWAVE PASSES BETWEEN 1300 AND 1400 UTC...INCLUDING
SSMI...SSMIS...QUIKSCAT...AND WINDSAT ALL SHOWED THAT THE LOW-LEVEL
CENTER WAS A LITTLE FARTHER NORTH THAN ANALYZED IN THE PREVIOUS
ADVISORY. THE LOW-LEVEL CENTER IS NOW A LITTLE EASIER TO FIND
DUE TO THE THINNING CONVECTIVE OVERCAST...AND CONFIDENCE IN THE
INITIAL MOTION ESTIMATE OF 310/06 IS A LITTLE HIGHER. THE TRACK
FORECAST PHILOSOPHY REMAINS UNCHANGED. MARTY WILL TURN TOWARD THE
WEST-NORTHWEST AND EVENTUALLY TOWARD THE WEST PRIOR TO DISSIPATION
AS IT FEELS THE INFLUENCE OF THE LOW-LEVEL RIDGE TO ITS NORTH. THE
OFFICIAL FORECAST IS ADJUSTED NORTH OF THE PREVIOUS PACKAGE DUE TO
THE INITIAL POSITION...AND TRENDS TOWARD THE FASTER TVCN MODEL
CONSENSUS BY 48 HOURS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 18/2100Z 21.1N 115.2W 35 KT
12HR VT 19/0600Z 21.7N 116.2W 30 KT
24HR VT 19/1800Z 22.4N 117.7W 30 KT
36HR VT 20/0600Z 22.6N 119.5W 25 KT...REMNANT LOW
48HR VT 20/1800Z 22.6N 121.5W 20 KT...REMNANT LOW
72HR VT 21/1800Z...DISSIPATED
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FORECASTER BRENNAN
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